1. Field of the Invention
The present invention relates to a nozzle used in a liquid and a foreign matter removing device provided with the nozzle.
2. Description of the Related Art
After a vehicle body is subjected to a predetermined welding process, the vehicle body is generally subjected to a coating pretreatment including a washing treatment, a degreasing treatment, a surface control treatment and a chemical conversion treatment. The vehicle body is then subjected to electrodeposition coating, intermediate coating and top coating.
In a coating pretreatment, a vehicle body is dipped in each tank of multiple tanks (dip tank) filled with treatment liquids in order. As a result, foreign matter which is stuck on the vehicle body such as iron powder or spatter is removed from the vehicle body, and the foreign matter settled in the treatment liquids is arranged on the bottom of each tank.
The electrodeposition coating is performed by dipping the vehicle body in a tank filled with a treatment liquid including electrodeposition paint. At this time, a pigment composition of the electrodeposition may be settled and arranged on the bottom of the tank.
However, foreign matter or a pigment composition (may be refereed to just as “foreign matter” including a pigment composition hereinafter) arranged on the bottom of the tank may be whirled up by the movement of the vehicle body in the treatment liquid or by natural convection current of the treatment liquid and may be stuck on the vehicle body. The foreign matter stuck on the vehicle body may cause painting defect.
To solve the problem, there are foreign matter removing devices for removing foreign matter arranged on the bottom of a tank outside the tank. Such a foreign matter removing device includes, for example, a hopper which is provided on the bottom of the tank for collecting foreign matter; a plurality of nozzles which injects a treatment liquid toward the hopper in a treatment liquid stored in a tank to collect the foreign matter in the hopper; a circulation pathway for discharging the treatment liquid which contains the foreign matter from the tank via the hopper and separates and returns only the treatment liquid to the nozzle. With such a foreign matter removing device, it is possible to remove the foreign matter settled on the bottom of the tank outside of the tank, which prevents the foreign matter from stacking on the vehicle body in the tank.
An ejector nozzle (see Japanese utility model application No. H03-43240) and a sectorial jetting nozzle (see Japanese patent application publication No. 2007-144377) have been conventionally known as a nozzle used in a liquid.
These ejector nozzle and sectorial jetting nozzle have been known to agitate a liquid stored in a tank. More specifically, the ejector nozzle prevents an electrodeposition paint in an electrodeposition liquid stored in an electrodeposition bath from being settled. In this ejector nozzle, the injecting pattern of the electrodeposition liquid is substantially a conic shape due to its ejector action.
The sectorial jetting nozzle is used for removing a grinding dust included in a coolant which has been used for, for example, metallic processing, by using foam separation. The sectorial jetting nozzle includes a plurality of injection holes arranged in a fan shape so that a bubble-mixed stream is formed in a wide range in the coolant filled in a tank.
In such a foreign matter removing device, however, foreign matter needs to be collected in a hopper without whirling up the foreign matter arranged on the bottom of a tank. Thus, conventional nozzles (see Japanese utility model application No. H03-43240 and Japanese patent application publication No. 2007-144377) which agitate a liquid (the electrodeposition liquid or coolant) can not be used in the foreign matter removing device.
Furthermore, conventional nozzles which agitate a liquid can not move the foreign matter toward a hopper efficiently since direct advancing property of the jet stream in a liquid is weak in the conventional nozzles. In the conventional nozzles, if the amount of liquid supplied to the nozzle is increased to move the foreign matter toward the hopper efficiently, not only the amount of upflung foreign matter is increased but also the size of a pump which supplies a liquid to the nozzle becomes larger, which results in increase in the manufacturing cost of the foreign matter removing device.